1. Field of the Invention
The present invention relates to a diaphragm closing device for the focus depth confirmation of the electromagnetic operative control camera whose lens aperture mechanism is operated in accordance with the electromagnetic control system.
2. Description of the Prior Art
In the case of an automatic exposure control camera which is so designed that the aperture preset ring of the photographic lens is charged at the totally opened position every time in functional engagement with the winding up operation of the camera, the aperture preset ring is driven from the totally opened position to the most closed position by means of the shutter release operation and the aperture value (preset value) of the photographic lens is determined by means of the operation result in accordance with the photographic information. It is necessary to move the automatic aperture pin and to release the holding of the aperture preset ring in order to confirm the focus depth in advance before taking a photograph. This is because the aperture preset ring is held at the totally opened position when the photographic lens in the automatic exposure control (AE) camera so composed is in the wound up state. Namely, in order to confirm the focus depth, it is necessary to bring the aperture set ring out of the AE mark and set the ring at the desired aperture mark. Further, when the diaphragm closing operation is carried out for confirming the focus depth when the photographic lens is set at the automatic exposure control (AE) mark, misjudgment of the focus depth takes place because the photographic lens is automatically closed down to the smallest aperture position. Consequently, when the aperture ring is set at the AE mark in the case of the camera with electromagnetic aperture control system, it becomes necessary to provide a mechanism for making the diaphragm closing impossible by locking the diaphragm closing device at the side of the camera.
In the conventional camera, the conventional motion picture camera and so on, for the aperture mechanism of the photographic lens, the manual operation system with the aperture ring provided on the lens barrel or the automatic aperture system for mechanically closing the diaphragm down to the position controlled with the sealing angle of the finger of the exposure meter is mostly used. However, quite recently, a camera to which the electromagnetic aperture control system for instantaneously closing the diaphragm mechanism down to a certain predetermined value releasing the attractive efficiency of the magnet is applied has been proposed. Hereby, in the case of the conventional camera with the electromagnetic aperture control system as mentioned above, a magnet is usually provided between the electrical circuit for controlling the aperture and the aperture control mechanism in such a manner that the control operation of the electrical circuit for supplying the magnet with current is utilized.
In the case of the camera of the electromagnetic aperture control system it is necessary to make the operation time of the electrical circuit, the magnet and the aperture control mechanism as short as possible in order not to lose the shutter opportunity, for which purpose various proposals have been made. However, when the operation time is shortened, the precision of the aperture is generally lowered in such a manner that the exposure accuracy of the camera is lowered, which is inconvenient.
The present invention relates to the improvement of the camera of the Japanese Patent Application Sho 50-95120 applied for on Aug. 5, 1975 by the present inventors as the electromagnetic aperture control system free from the shortcomings of the camera of the conventional electromagnetic aperture control system in such a manner that the operation time of the aperture control mechanism is shortened while the exposure accuracy is increased as much as possible. The invention more particularly relates to the diaphragm closing device for the focus depth confirmation of the camera of the above mentioned electromagnetic aperture control system.